SV_MEETING_TITLE -- 11 Dec 2008

i'll scribe

<sandro> scribe: StellaMitchell

<ivan> :-(

sandro: Goal this meeting is to figure out the tasks and who will do them, but not to dig completely into all the technical details
... four topics of coordination, the first is probably simple
... first item: rdf:text

rdf:text

sandro: when it was published I said public comments should go to the public owl list

<ChrisW> take up item 1

chris: ask editors of rdf:text if they are willing to be the coordinators of public comments

sandro: in terms of last call and dependences, the OWL ? spec depends on this, and some RIF documents will also be dependent also

boris: is it ok to say in the spec that we sppport the rdf:text datatype, and if it changes later that will be ok
... use it in an opaque way, and so remove the dependency on the document. This applies to other datatype also.

daver: rdf:text is a different case from other datatypes

boris: when you say you change rdf:text, you are not chaning the satisfiability of any document

daver: yes, it would be an observable change
... ,Andy Seaborne sent an email about this

ivan: I don't see the problem

sandro: Andy's email sent to the public rdf:text list shows the problem
... we need to make sure now that rdf:text will be defined in an acceptable way - we can't assume it will happen in the future

<sandro> sandro; we need rdf:text to get to rec before anything that depends on it

<DaveReynolds> Andy's message: http://lists.w3.org/Archives/Public/public-rdf-text/2008OctDec/0032.html

<sandro> http://lists.w3.org/Archives/Public/public-rif-wg/2008Dec/0046.html

RIF OWL&RDF compatibility

jos: summarizing the above email
... I made 5 proposals (labelled P1 through P5) in the email

sandro: I don't understand the relationship between owl 1 full and owl 2 full
... I tentatively agree to proposal P1

chris: there was a change to OWL full in OWL2, but do we believe it to be insignificant?

<DaveReynolds> Similarly I see no problem with P1

<sandro> sandro: sounds like P1 is fine

jos, boris: yes

jos: summarized P2 and P3

<sandro> sandro: In OWL 2 you can't signal that you're not in OWL 1, so year, P2 and P3 make sense.

sandro: as I understand, you are not allowed to signal whether you're in OWL 1 and OWL 2

boris: P2 and P3 are ok with me'

<sandro> http://www.w3.org/2005/rules/wiki/SWC#Importing_RDF_and_OWL_in_RIF

jos: explaining IRIs of profiles. reference above.

sandro: note that these are not like OWL profiles

jos: does anyone disagree with P4?

<sandro> Jos: drop OWL Dl annotaiton

sandro: do we still need the annotation profile?

jos: no, would drop it.

sandro: conformance clause for owl says everyone has to implement rdf serializaiton for owl and they may implement the other ones

<sandro> sandro: I think leave it RDF/XML, but maybe add a note about other syntaxes.

jos: I don't have a strong opinion about allowing other syntaxes to be imported
... summarizing P5

<sandro> jos: "OWL DLP" would migrate to "OWL 2 RL"

boris: what is meant by a combination?

<DaveReynolds> Agree with P5 too

<sandro> P5 sounds good...

jos: (explained combination)

chris: why should DLP be dropped?

jos: OWL 2 RL is sort of the same thing

chris: but is not the same thing, so why should we drop DLP? Most OWL implementations are currently OWL 1

jos: I made up this DLP, it's not the one you are thinking of that people have implemented

<sandro> jos: no datatype support in Horrocks et al DLP. that's one of several differences.

<DaveReynolds> +1 with Jos

<ivan> +1 with Jos

chris: I'm not sure about dropping the DLP section from RIF, RDF and OWL compatibility document, I need to think about it more

zhe: when I started in the OWL WG, we had a DLP but the working group decided to drop it, and then later OWL 2 RL was defined, so I support dropping DLP

sandro: we'll investigate before deciding

3. The list of datatypes (aside from RL) (10 minutes)

<sandro> http://www.w3.org/2005/rules/wiki/DTB#Symbol_Spaces

<sandro> http://www.w3.org/2007/OWL/wiki/Syntax#Datatype_Maps

The list of datatypes

chris: we should coordinate on the set of datatypes, there is no real rationale for having different sets in RIF and OWL

<DaveReynolds> http://www.w3.org/2005/rules/wiki/OWLRL#Datatypes_supported

boris: it's not just the list of types, but we have adapted the semantics of some of the datatypes, e.g. for double

sandro: from what I understand, the same reasons should apply to RIF, and RIF should use the same definitions

<sandro> sandro: It sounds like there's nothing OWL specific here.... so RIF should also use owl:real, etc?

boris: RIF has casts between datatypes, and OWL does not

<sandro> boris: imagine weight has range integer, and then someone gives a value of "70"^^xs:double --- that's inconsistent.

boris: giving example of how casts could results in inconsistency: range of certain property is integer, weight, someone puts 70.0 as double so

<sandro> boris: In RIF you can do a cast, which allows you to hack around this situation.

boris: OWL doesn't support any functions

chris: so we could adopt a common set of datatypes, where OWL doesn't include the built-ins and RIF does

dave: are you saying that owl real isn't separated from the integers?

<sandro> boris explains owl:real and owl:realPlus

boris: owl real is the umbrella for all the numeric datatypes

chris: I'm trying to understand if there needs to be an actual difference in the set of datatypes
... such that we can share datatypes and RIF supports built-ins while OWL doesn't

<DaveReynolds> dave: don't understand how "1.1"^^owl:real can be both a double and decimal, they are different

boris: with our datatype definitions, we are trying to be more user friendly

chris: so, owl:real is a superclass?

boris: yes

chris: ok, so there is a difference in some of the datatype definitions
... owl approach breaks xml schema compatibility

boris: we did talk to xml schema people and they weren't averse to this, and supported it

<Zhe> sure

<sandro> meeting extended until 20 after the hour.

chris: so that feedback from xml schema group may help address the concerns of the production rule concerns in RIF

jos: these issues with value spaces are subtle and I would be ok with changing to the way OWL is doing it, but I think the long list of datatypes is a problem

dave: owl:real sounds like a problem to me. people use decimal and double for specific reasons
... when you express something you need to know what it is

boris: you do always know what it is
... small problem might be when you say the range must be an integer and then put a double constant there that is actually an integer

<sandro> boris: The only question is when you do class reasoning on types....

boris: in owl, we say you have not violated the range constraint in that case

<sandro> sandro: in RIF this comes up with is-this-an-integer applied to "70"^^xs:float or "70"^^xs:decimal.

sandro: RIF needs a test case about this, to get feeback from the WG

jos: what sandro wrote above, in OWL would you interpret those as different objects?

boris: no, we interpret them all as the integer 70
... but 0.1 double is not the same as 0.1 decimal, because 0.1 double gets rounded

<sandro> boris: "0.1"^^xs:float is NOT the same as "0.1"^^xs:decimal, because of rounding in the internal representation. We don't lose any precision.

<sandro> boris "70"^^xs:float and "70"^^xs:decimal are IDENTICAL in OWL -- they are both the number 70.

boris: xml schema defines equality differently from identity

dave: if you put in value that is larger than the mantissa for xs:float, what happens?

boris: it would follow the mapping giving in xml schema, I don't know what it is off the top of my head

<ChrisW> is 100000000000045 (assuming that is beyond the range of float) a *float*

<sandro> boris: This gets messy, comparing doubles with integers, etc, but we did manage to implement this in Hermit.

chris: question - is the number above considered a float?

<DaveReynolds> The test case is whether "100000000000045 "^^xsd:float = "100000000000045"^^xsd:integer, the answer should be no.

boris: yes, it is. but it might get rounded into another float

<Zhe> or "1.0000000000000001"^^float = "1"^^integer, answer is yes

4. OWL RL (20 minutes)

sandro: summarize items from agenda

<sandro> -- aligning the list of datatypes

<sandro> -- providing the rules as a RIF Core document

<sandro> -- any issues with the ruleset itself

<sandro> -- rules/code to check the ontology

dave: first item: since datatypes don't align, we couldn't express OWL RL in RIF

<sandro> DaveReynolds: it would be ideal if the OWL-RL datatypes were the intersection of OWL and RIF-Core datatypes.

sandro: it will be easier to reduce the list of datatypes in OWL-RL than in the other OWL profiles
... customers would want RIF and OWL to be aligned

dave: normalized strings

jos: why in OWL-RL can you not allow datatypes with finite value spaces

boris: (missed answer)
... maybe in OWL-RL that restriction is not necessary
... we do in EL and QL

<sandro> boris: Ah, the finiteness restriction on OWL-RL might not be necessary.

sandro: Dave, are you willing to see if we can get these extra datatypes added to RIF Core?

dave: I think it will be mostly up to Axel - I see no value in having things like ncname

boris: we kept it for consistency, so we didn't have to explain why we excluded it

dave: RIF took opposite approach: each inclusion had to be justified

jos: owl:rational would be something completely new for RIF

<sandro> sandro: lets have RIF look at the RL datatype list and push back where necessary.

sandro: RIF needs to look at list of OWL datatypes and see which ones can go in RIF core and then ask OWL to remove the other ones

chris: does OWL 2 support all the RIF datatypes?

boris: there are 2 xquery, duration related ones that we don't support

<sandro> DaveReynolds: I'm fine with my document being folded into Jos'

sandro: We need to decide what to do with the "OWL 2 RL in RIF" document

chris: in Dave's document there is the RIF core rule implementation of OWL 2 RL and there is a lot of background information. How about just taking the RIF Core implementation and making that the OWL RL profile?

<sandro> bmotik: We're perfectly aware that a naive implementation of the OWL RL rules will have poor performance. But we wanted the semantics to be very clear.

<sandro> bmotik: eg quadratic number of literals, but you'd need builtins and NAF, etc.

<sandro> bmotik: and we didnt want to go there.

chris: I don't understand your point. I'm suggesting you express the ruleset in RIF Core syntax.

<sandro> chrisw: How about using RIF Core Presentation Syntax to express the OWL-RL rules?

boris: ok, I understand the question. I'm not sure right now, have to consult with others.

chris: I think if we solve the datatype issues, then I think it would just be a small change to the syntax

dave: owl uses ellipsis, makes it easier to read, less explicity about what to implement

<sandro> jos: my embedding stuff does not operate on T(s,p,o) but on translation to RIF. very different.

<sandro> Zhe: I don't want to take out the RDF-oriented rule in the OWL-RL spec, but I like adding RIF stuff.

boris: my personal opinion is that changing the actual ruleset would be painful for OWL
... and require extensive negotiations
... but changing syntax may be ok

<ChrisW> "Life IS pain, princess. Anyone who says otherwise is selling something" - Princess Bride

<DaveReynolds> :-)

<Zhe> thanks

<christine> bye

<sandro> StellaMitchell, thanks so much for scribing.

you're welcome

<ChrisW> +1 thanks

- DRAFT -

SV_MEETING_TITLE

11 Dec 2008

Attendees

Contents

rdf:text

RIF OWL&RDF compatibility

3. The list of datatypes (aside from RL) (10 minutes)

The list of datatypes

4. OWL RL (20 minutes)

Summary of Action Items

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